Hologram-type polarized-light splitting element

ABSTRACT

A hologram polarized light separator which does not generate heat when absorbing an unnecessary polarized component, does not degrade, has a high degree of separation, is lightweight, and allows a system to be of a small scale. Incident natural light (I) incident normally on the surface of a hologram ( 1 ) is separated into a first linearly polarized light (E 1 ) traveling without being diffracted and a second linearly polarized light (E 2 ) polarized perpendicularly to the direction of polarization of the first linearly polarized light (E 1 ). The first linearly polarized light (E 1 ) passes through a substrate glass ( 2 ) as it is; the second linearly polarized light (E 2 ) undergoes internal total reflection at the glass-air boundary line and cannot go out to the output side of the separator. Therefore, the separator can allow only one of the polarized components of the incident natural light to travel in a predetermined direction. A liquid crystal projection display comprising the separator is also disclosed.

This application is the national phase under 35 U.S.C. § 371 of PCTInternational Application No. PCT/JP99/00441 which has an Internationalfiling date of Feb. 3, 1999, which designated the United States ofAmerica.

TECHNICAL FIELD TO WHICH THE INVENTION PERTAINS

The present invention relates to a polarizing element for taking onlyunidirectional plane-polarized light out of natural light being socalled indefinitely polarized light.

BACKGROUND OF THE INVENTION

A conventional liquid crystal projector (LC projection display) isprovided with a liquid crystal display panel that necessarily uses apolarizing plate for cutting off unnecessary components from lightoutgoing therefrom for forming an image. However, a conventionaldichroic type polarizing plate absorbs unnecessary light that becomesheat energy for internally heating the plate, causing prematuredeterioration of the plate. Accordingly, recent LC projectors use,instead of the polarizing plate, a polarized-beam splitter having athin-film coat deposited thereon or diffraction type polarizing elementsdisclosed in Japanese Laid-Open Patent Publication No. 61-240204 and No.62-249107 and Japanese Patent No. 2594548 (Japanese Laid-Open PatentPublication No. 63-26604).

However, the above described conventional methods have the followingdrawbacks:

The thin-film deposited type polarized-beam splitter is constructed oftwo glass-made prisms bonded to each other, which is thick and,therefore, is not so small and light to be usable in liquid crystalprojectors. Namely, the use of this type beam splitter as a polarizingplate of a light outputting portion of a liquid crystal projectornecessarily elongates a back focal length of a projector lens and,thereby, causes the need for increasing a diameter of the projectionlens, a projection distance and a weight of a whole optical system.

The application of the diffraction type polarizing element described inJapanese Laid-Open Patent Publication No. 61-240204 as an emergent-sidepolarizing plate cannot produce a well-contrasted clear image since theelement cannot completely split polarized light, causing leakage oflight. The diffraction type polarizing element described in JapanesePatent No. 2594548 (Japanese Laid-Open Patent Publication No. 63-26604)as compared with the element of Japanese Laid-Open Patent PublicationNo. 61-240204 has a higher degree of polarized-beam separation, a highercontrast and a smaller wavelength-dependent diffraction difference thatis estimated at a value of dispersion of refracting media. This element,however, cannot have a large diffraction angle because of a smalldifferential refractive index of its diffraction grating. The use ofthis element as a polarizing plate on the emergent side of a liquidcrystal projector elongates a back focal length of a projection lens.The hologram-type polarized-light splitting element described inJapanese Laid-Open Patent Publication No. 62-249107 has an excellentpolarized-light splitting ability and a large splitting angle but has anincident light falling thereto at a large angle to a line perpendicularto the hologram plane, requiring a large working space. Therefore, theuse of this element as an emergent-side polarizing plate in a liquidcrystal projector may also require elongation of a back focal distanceof a projection lens.

In view of the foregoing, the present invention was made to provide ahologram polarized-light splitting element capable of effectivelysplitting polarized light with no absorption of unnecessary light, i.e.,eliminating the possibility of being heated by absorbed light and ofdeterioration by heat, which element is so light and small to form acompact optical system. The present invention is also directed to acompact liquid crystal display device using the above-described element.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a hologram-typepolarized-light splitting element made of a glass substrate with ahologram formed thereon, which element can split incident light into twoplane-polarized (linearly polarized) components having polarizationdirections perpendicular to each other by allowing one of the componentsto pass the hologram after diffraction and the other component to passstraight without diffraction, and which element can select and emit onlythe non-diffracted plane-polarized component of the light in thespecified direction and, at the same time, can further reflect thediffracted plane-polarized component at least once at a boundary betweenthe glass substrate and medium surrounding the element. This element canthus split incident light at high accuracy with no absorption ofunnecessary light component that may become thermal energy as observedin the conventional dichroic absorption type light polarizing element,thereby it can maintain high reliability of performance for its longservice life. The element is a thin plate that can form a very compactand light optical system in which it can be disposed at right angles toan optical axis of the system.

Another object of the present invention is to provide a hologram-typepolarized-light splitting element made of a glass substrate with ahologram formed thereon, in which the hologram is given diffractionproperties for obtaining diffracted plane-polarized light andnon-diffracted plane-polarized light from a p-plane-polarized componentand a s-plane-polarized component, respectively, of incident light at ahigh separation degree by diffracting the former component to travel inthe direction making a separation angle of 60 degrees with thetravelling direction of the latter.

Still another object of the present invention is to provide ahologram-type polarized-light splitting element made of a glasssubstrate with a hologram formed thereon, in which the hologram is givendiffraction properties for obtaining diffracted plane-polarized lightand non-diffracted plane-polarized light from a p-plane-polarizedcomponent and a s-plane-polarized component, respectively, of incidentlight at a high separation degree by diffracting the former component totravel in the direction making a separation angle of 48.2 degrees withthe travelling direction of the latter.

A further object of the present invention is to provide a liquid crystalprojection display having a compact optical system with a shortback-focal distance of a projection lens, which comprises a liquidcrystal panel and at least a first polarizing element and a secondpolarizing element on the incident side and the emergent side,respectively, of the liquid crystal panel, in which each polarizingelement is a hologram-type polarized-light splitting element accordingto the present invention, which element can split incident light intotwo polarized components at high contrast with no fear of being heatedby light absorption and has no need for elongating a back focal lengthof its projecting lens.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view for explaining how incident light is split intodiffracted light and transmitted light by means of a hologram-typepolarized-light splitting element.

FIG. 2 is a view for explaining the principle of setting diffractingproperties for a hologram-type polarized-light splitting elementaccording to the present invention.

FIG. 3 is a schematic construction view of a hologram-type polarizelight splitting element embodying the present invention.

FIG. 4 is a view for explaining how to prepare a hologram-typepolarized-light splitting element shown in FIG. 3.

FIG. 5 is a schematic construction view of another hologram-typepolarized-light splitting element embodying the present invention.

FIG. 6 is a view for explaining how to prepare a hologram-typepolarized-light splitting element shown in FIG. 5.

FIG. 7 is a schematic construction view of essential portions of aliquid crystal projection display according to an embodiment of thepresent invention.

FIG. 8 is a schematic construction view of essential portions of aliquid crystal projection display according to another embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A hologram-type polarized-light splitting element according to thepresent invention is a glass substrate with a transmitting-type hologramformed thereon for diffracting one of plane-polarized components ofnatural incident light vertically entering the element and allowing theother plane-polarized component perpendicular to the former component topass therethrough without diffraction. The hologram has a specifiedgrating angle, width, thickness and refractive index range so as todiffract polarized light at a specified angle necessary for obtaininghigh diffraction efficiency and totally reflecting light from aglass-to-air boundary of the glass substrate.

The preferred embodiments of the present invention will be describedbelow with reference to the accompanying drawings.

FIG. 1 is a view for explaining light rays diffracted and transmitted bya hologram-type polarized-light splitting element according to thepresent invention, which element comprises a hologram 1 and a grasssubstrate 2. In FIG. 1, there is shown natural incident light I, firstplane-polarized light (transmitted light) E₁ and second plane-polarizedlight (diffracted light) E₂.

FIG. 2 is a view for explaining a diffraction angle selecting methodapplied to the hologram-type polarized-light splitting element accordingto the present invention, where d is a hologram thickness, θ is an angleof incident light and θs is an angle of emergent light with respect toan imaginary line perpendicular to the hologram surface.

A hologram-type polarized-light splitting element according to thepresent invention is constructed of a glass substrate 2 with a hologram1 formed thereon. The hologram 1 is a volume-type phase hologram whosematerial and thickness are selected so that it achieves possibly highestdiffraction efficiency. The hologram 1 has such a preset diffractionangle that it may most accurately split natural light into twoplane-polarized components whose polarization directions areperpendicular to each other. One component is first plane-polarizedlight E₁ passing the hologram 1 without being diffracted and the otheris second plane-polarized light E₂ diffracted by the hologram 1.

Referring to FIG. 2, the concept of setting diffraction properties ofthe hologram will be described below:

According to the Kogelnik's coupled-wave theory, diffraction efficiencyη of the volume-type phase hologram can have the following expression(1) on the condition there is no absorption by material and Bragg'scondition is satisfied.

η=sin²(ν)  (1)

$\begin{matrix}{\nu = \frac{\kappa \quad d}{\sqrt{\cos \quad {\theta cos\theta}_{s}}}} & (2)\end{matrix}$

An angle θ made by light not diffracted inside the hologram with theline perpendicular to the surface of the hologram is equal to an angle θof incident light. In the equation (2), k is called a couplingcoefficient. Polarized light p and polarized light s may have differentcoupling coefficients k_(p) and k_(s) respectively.

κ_(p)={fraction (πn₁+L /λ)} cos(θ−θ_(s))  (3)

κ_(s)={fraction (πn₁+L /λ)}  (4)

Consequently, p-plane-polarized light and s-plane-polarized light havedifferent values of diffraction efficiency.

A p-plane-polarized light diffracting hologram-type polarized-lightsplitting element may have diffraction efficiency ηp =1 forp-plane-polarized light, and diffraction efficiency ηs=0 fors-plane-polarized light. Therefore, ν=π/2 and ν=π are obtained accordingto Equation (1). From Equations (2), (3) and (4), the followingcondition can be derived.

|θ−θ_(s)|=60°  (5)

θ is equal to 0 when incident light enters the hologram perpendicularlyto the top surface of the hologram. When θs is equal to 60°, thediffraction efficiency can be set to 1 for s-plane-polarized light andthe diffraction efficiency can be set to 0 for p-plane-polarized light.In this instance, the first plane-polarized light E₁ becomess-plane-polarized light and the second plane-polarized light E₂ becomesp-plane-polarized light as shown in FIG. 1.

As an example of a s-plane-polarized light diffracting hologram-typepolarized-light splitting element, values for s-plane polarized lightand p-plane-polarized light may satisfy the condition=and=3/2respectively. Similarly to Equation (5), the following condition isobtained:

|θ−θ_(s)|=48.2°  (6)

Accordingly, the diffraction efficiency values 1 and 0 are obtained fors-plane-polarized light and p-plane-polarized light respectively when θis 0 and θs=48.2°. In this case, the first plane-polarized light E₁becomes p-plane-polarized light and the second plane-polarized light E₂becomes s-plane-polarized light as shown in FIG. 1.

The natural light I entering the hologram 2 at the right angles theretois split into the first plane-polarized light E₁ passing the hologramwithout being diffracted and the second plane-polarized light E₂ isdiffracted at the specified angle by the hologram 2. The polarizationdirection of the second plane-polarized light E₂ is normal to that ofthe first plane-polarized light. The first non-diffractedplane-polarized light E₁ passes through the glass substrate 2. On theother hand, the second diffracted plane-polarized light E₂ travels inthe glass substrate 2 and is completely reflected into the glass from aglass-to-air boundary, if the glass substrate 2 has a refractive index(ng) of 1.52, with a refraction angle exceeding the critical angle of41° at the boundary. Therefore, the plane-polarized splitting elementcan selectively output only one of two plane-polarized components ofincident natural light in a specified direction.

FIG. 3 is a schematic construction view of a hologram-typepolarized-light splitting element embodying the present invention. InFIG. 3, numeral 11 designates a hologram and numeral 12 designates aglass substrate.

FIG. 4 is a view for explaining how to prepare the hologram-typepolarized-light splitting element shown in FIG. 3. There is shown aphotosensitive material 11 e, a first trapezoidal prism 13 a, a secondtrapezoidal prism 13 b, objective light O and reference light R. Otherelements similar to those shown in FIG. 3 are given the same referenceletters and symbols.

As described above with reference to Equation (5), the hologram cansplit incident plane-polarized light into two components by diffractingp-plane-polarized light at an angle of 60° to a non-diffracteds-plane-polarized light. A hologram made of photosensitive material,e.g., photo-polymer (n=1.54) having thickness (d) of 12.2 microns willbe described below. The hologram is prepared by exposing thephotosensitive material through an optical system shown in FIG. 4. Thefirst and second trapezoidal prisms 13 a and 13 b have a trapezoidalsection having an angle of 61.3° at one of four corners and are made ofthe same glass material (ng=1.52) that used for making the glasssubstrate 12. The trapezoidal prisms 13 a and 13 b are symmetricallyattached with matching oil to opposite surfaces of a holographic dryplate that is a photosensitive material 11 e made of photo-polymer andattached to the glass substrate 12. The dry plate is exposed toreference light R and objective light O coherent with the referencelight R in such a way that light rays R and O enter the oblique surfaceof the prism 13 a, making an angle of 63.1° with a line perpendicular tothe glass substrate 12 as shown in FIG. 4. The objective light O isrefracted at the boundary from the first trapezoidal prism 13 a to thephotosensitive material 11 e, making an angle of 60° with the normal ofthe hologram, and interferes with the reference light R to forminterference fringes inside the photosensitive material 11 e. Thetrapezoidal prisms 13 a and 13 b are removed, then the exposedphotosensitive material is processed to obtain a hologram-typepolarized-light splitting element. In this instance, the preparedelement is supposed to have the hologram with grating fringes recordedtherein with a refractive index amplitude n1 of 0.03. The spacingbetween grating fringes formed in the hologram is 0.33 microns when thehologram was exposed to the light of 514 nm. The normal line of thegrating fringes makes an angle of 60° with the normal line of thehologram.

When natural light having a wavelength of 514 nm enters the preparedhologram-type polarized-light splitting element along the normal line ofthe glass substrate 12, it can be split into two plane-polarizedcomponents s and p: the p-plane- polarized component is diffracted bythe hologram 11 and totally reflected from the glass-to-air boundary,while the s-plane-polarized component travels straight (without beingdiffracted) and passes the glass substrate 12 as shown in FIG. 3. Thewavelength range of the element can be expanded by overlaying aplurality of holograms or conducting multiple exposure of thephotosensitive element.

FIG. 5 is a schematic construction view of another hologram-typepolarized-light splitting element embodying the present invention. InFIG. 5, there is shown a hologram 21 and a glass substrate 22. FIG. 6 isa view for explaining how to prepare the hologram-type polarized-lightsplitting element of FIG. 5. In FIG. 6, there is shown a photosensitivematerial 21 e, a first trapezoidal prism 23 a, a second trapezoidalprism 23 b, an objective light O and reference light R. Other elementssimilar to those of FIG. 5 are given the same reference characters.

As described before with reference to Equation (6), the hologram cansplit incident light into two plane-polarized light components s and pwhen it may diffract the s-plane component at an angle of 48.2° withrespect to the non-diffracted p-plane component. A hologram made ofphotosensitive material, e.g., photo-polymer (n=1.54) having thickness(d) of 12.2 microns will be described below. The hologram is prepared byexposing the photosensitive material 21 e through an optical systemshown in FIG. 6. The first and second trapezoidal prisms 23 a and 23 bhave a trapezoidal section having an angle of 49° at one of four cornersand are made of the same glass material (ng=1.52) that used for makingthe glass substrate 22. The trapezoidal prisms 23 a and 23 b aresymmetrically attached with matching oil to opposite surfaces of aholographic dry plate that is the photosensitive material 21 e made ofphoto-polymer and attached to the glass substrate 22. The dry plate isexposed to reference light R and objective light O coherent with thereference light R so that light rays R and O enter the oblique surfaceof the prism 13 a making an angle of 48.2° with a line perpendicular tothe glass substrate 22 as shown in FIG. 6. The objective light O isrefracted at the boundary from the first trapezoidal prism. 23 a to thephotosensitive material 21 e, making an angle of 65.9° with the normalof the hologram, and interferes with the reference light R to forminterference fringes inside the photosensitive material 21 e. Thetrapezoidal prisms 23 a and 23 b are removed, then the photosensitivematerial is processed to obtain a hologram-type polarized-lightsplitting element. In this instance, the prepared element is supposed tohave a hologram with grating fringes recorded therein with a refractionfactor amplitude n1 of 0.03. The spacing between grating fringes formedin the hologram is 0.41 microns when the hologram was exposed to thelight of 514 nm. The normal line of the grating fringes makes an angleof 65.9° with the normal line of the hologram.

When natural light having a wavelength of 514 nm enters the preparedhologram-type polarized-light splitting element along the normal line ofthe glass substrate 22, it can be split into two plane-polarizedcomponents s and p: the p-plane-polarized component is diffracted by thehologram 21 and completely reflected from the glass-to-air boundary,while the s-plane-polarized component travels straight (without beingdiffracted) and passes the glass substrate 22 as shown in FIG. 5. Thewavelength range of the element can be expanded by overlaying aplurality of holograms or conducting multiple exposure of thephotosensitive element. FIG. 7 is a schematic construction view showingessential portions of a liquid crystal projection display according toan embodiment of the present invention. In FIG. 7, the liquid crystaldisplay comprises a liquid crystal display panel 31, a firsthologram-type polarized-light splitting element 32 a and a secondhologram-type polarized-light splitting element 32 b. In thisembodiment, the liquid crystal display panel 31 is provided with thefirst and second polarized-light splitting elements 32 a and 32 bdisposed before and after liquid crystal display panel 31. Natural lightfrom a light source (not shown) through an optical system (not shown)enters the first hologram polarized-light splitting element 32 a bywhich it is split into two plane-polarized components whose polarizationdirections are perpendicular to each other. One component is diffractedby the hologram and then totally reflected from the glass substrate, notreaching the liquid crystal display panel 31. The other component passesthrough the first hologram-type polarized-light splitting element 32 aand enters the liquid crystal display panel 31 in which theplane-polarized light is modulated. An unnecessary image-light componentis further diffracted by the second hologram polarized-light splittingelement 32 b and then totally reflected. The liquid crystal projectiondisplay according to the present invention can be free from heataffection and aging because it uses the hologram-type polarized-lightsplitting element with no absorption of unnecessary light, instead ofconventional dichroic type polarizing plate, as polarization elementsbefore and after the liquid crystal display panel.

FIG. 8 is a schematic construction view showing an essential portion ofa liquid crystal projection display according to another embodiment ofthe present invention. In FIG. 8, the liquid crystal display comprises aliquid crystal display panel 41, a hologram-type polarized-lightsplitting element 42, an incident-side polarizing plate 43 a and anemergent-side polarizing plate 43 b. In this embodiment, the liquidcrystal display panel 41 is provided with the incident-side polarizingplate 43 a disposed in the front thereof and the emergent-sidepolarizing plate 43 b disposed in the rear thereof. Furthermore, ahologram-type polarized-light splitting element 42 is disposed betweenthe liquid crystal display panel 41 and the emergent-side polarizingplate 43 b. Natural light emitted from a light source (not shown)through an optical system (not shown) enters the incident-sidepolarizing plate 43 a in which one of the two plane-polarized lightcomponents having different polarization directions perpendicular toeach other is absorbed and the other component is allowed to passtherethrough and enter the liquid crystal display panel 41 in which theplane-polarized light is then modulated. An unnecessary polarized-lightcomponent is diffracted by the hologram-type polarized-light splittingelement 42 and then completely reflected from the boundary, not reachingthe emergent-side polarizing plate 43 b that can be thus protected frombeing heated by absorption of the unnecessary light and, therefore, fromheat-aging.

THE INDUSTRIAL APPLICABILITY OF THE INVENTION

According to the present invention, it is possible to provide ahologram-type polarized-light splitting element that can accuratelysplit polarized light into two plane-polarized components by means of ahologram having adapted diffraction properties and can operate withoutbeing heated due to absorption of light and can maintain highreliability of its performance for a long service life because it doesnot absorb unnecessary light components, in distinction fromconventional dichroic absorption type polarizing elements. Furthermore,the element is a thin plate that can form a compact optical systembecause it can be disposed at right angles to the optical axis thereof.

According to the present invention, it is also possible to provide ahologram with preset conditions of diffraction properties necessary forsplitting polarized-light at high degree of separation.

According to the present invention, it is further possible to provide aliquid crystal display having a compact optical system that can splitincident polarized light into components without being heated because itdoes not absorb unnecessary light and does not require elongation of theback focal length of a projection lens.

What is claimed is:
 1. A hologram-type polarized-light splitting elementcomprising a glass substrate with a hologram framed thereon a firstsurface, which element splits incident light into two plane-polarizedcomponents perpendicular to each other by allowing one of the componentsto pass the hologram after diffraction and the other component to passtherethrough without diffraction, and which element selectively outputsonly the non-diffracted plane-polarized component of the light through asecond surface opposite the first surface in a specified direction and,at the same time, totally reflects the diffracted plane-polarizedcomponent at least once at a boundary between the second surface of theglass substrate and medium surrounding the element.
 2. A hologram-typepolarized-light splitting element as defined in claim 1, wherein thehologram is given diffraction properties for obtaining diffractedplane-polarized light and non-diffracted plane-polarized light from ap-plane-polarized component and a s-plane-polarized component,respectively, of incident light at a high separation degree bydiffracting the former component to travel in a direction making asplitting angle of 60 degrees with a direction of the latter.
 3. Ahologram-type polarized-light splitting element as defined in claim 1,wherein the hologram is given diffraction properties for obtainingdiffracted plane-polarized light and non-diffracted plane-polarizedlight from a p-plane-polarized component and a s-plane-polarizedcomponent, respectively, of incident light at a high separation degreeby diffracting the former component to travel in a direction making aseparation angle of 48.2 degrees with a direction of the latter.
 4. Aliquid crystal projection di splay comprising a liquid crystal panel andat least a first-polarizing element and a second-polarizing element onthe incident side and the emergent side, respectively, of the liquidcrystal panel, wherein the first and/or second-polarizing element is thehologram-type polarized-light splitting element of claim 1 or 2 or
 3. 5.A polarized light-splitting device, comprising: a glass substrate; ahologram formed on a first surface of the glass substrate, wherein anincident light passing into the hologram and the glass substrate issplit into two plane-polarized components, wherein only one of the twoplane-polarized components passes through a second surface of the glasssubstrate, and the other one of the two plane-polarized components isprevented from passing through the glass substrate at the second surfaceand is internally reflected in the glass substrate at the secondsurface.
 6. The device of claim 5, wherein the two plane-polarizedcomponents are polarized perpendicular to each other.
 7. The device ofclaim 5, wherein said other one of the two plane-polarized components isdiffracted into the glass substrate at the first surface.
 8. The deviceof claim 7, wherein said other one of the two plane-polarized componentsis diffracted into the glass substrate at an angle of 60 degrees withrespect to a normal to the first surface.
 9. The device of claim 7,wherein said other one of the two plane-polarized components isdiffracted into the glass substrate at an angle of 48.2 degrees withrespect to a normal to the first surface.
 10. A liquid crystalprojection display, comprising: a liquid crystal panel; a firstpolarized light-splitting device on an incident side of the liquidcrystal panel; and a second polarized light-splitting device on anemergent side of the liquid crystal panel, wherein at least one of thefirst and second polarized light-splitting devices is the polarizedlight-splitting device of claim
 5. 11. A method of using one or morehologram-type polarized light-splitting devices in a liquid crystalprojection display, wherein the hologram-type polarized light-splittingdevice includes a hologram formed on a glass substrate, the methodcomprising: splitting an incident light into two plane-polarizedcomponents in a hologram-type polarized light-splitting device; passingonly one of the two plane-polarized components through a glass substrateof the hologram-type polarized light-splitting device and preventingoutput of the second plane-polarized component; and modulating said onlyone of the two plane-polarized components in a liquid crystal panel toform a modulated light beam.
 12. The method of claim 11, furthercomprising: passing the modulated light beam through a secondhologram-type polarized light-splitting device; and removing anundesired polarization from the modulated light beam.
 13. Ahologram-type polarized-light splitting element comprising a glasssubstrate with a hologram formed thereon, which-element is capable ofsplitting incident light into two plane-polarized componentsperpendicular to each other by allowing one of the components to passthe hologram after diffraction and the other component to passtherethrough without diffraction, and which element selectively outputsonly the non-diffracted plane-polarized component of the light in aspecified direction and, at the same time, prevents output of thediffracted plane-polarized component by totally reflecting thediffracted plane-polarized component at a boundary between the glasssubstrate and medium surrounding the element.